Field of the Invention: The present invention relates generally to automatic nailing devices and more particularly to an automatic stitch nailing device for repetitively positioning and nailing transverse slats onto parallel longitudinally advancing stringers.
Description of the Prior Art: The economics required in manufacturing practices today, demand that automatic devices replace manual labor in certain repetitive manufacturing operations. This demand is particularly noticeable in the construction of such articles as docks, pallets, certain types of fences, etcetera, having assembly steps involving the common operation of repeatedly securing or nailing a plurality of parallel slats to at least one side of a plurality of parallel, spaced apart stringers. Another such example is in the construction of certain types of wood frames which contain transverse members secured to longitudinal stringers and assembled in a given pattern to form a frame.
Known prior art devices for performing such tasks have attacked the problem by first collecting and positioning the individual parts of the article of manufacture and thereafter conveying the pre-positioned parts to a plurality of nailing heads for the final securing operation. This, of course, requires complicated jigs and clamping devices for holding the individual parts in their correct positions relative one another during both the conveying and the nailing operations. This pre-assembly concept also requires the use of manual labor to assemble the parts in their aligned positions, or alternatively, complicated mechanical or electromechanical mechanisms must be provided to accomplish the pre-assembly operations.
Another approach toward solving the automation problem, which applies particularly to the construction of pallets has been to provide a machine which advances a plurality of stringers extending on a conveyor transversely of the direction of their advancement, into underlying engaging relationship with a plurality of deck boards stacked in a hopper in predetermined relationship to one another and extending longitudinally of the conveyor. Thereafter, the stringers and the bottom layer of deck boards are unitarily advanced beneath a nailing mechanism with the remaining vertically stacked deck boards in the hopper serving to hold the advancing stringers and engaged deck boards in position during the nailing process. This arrangement not only requires the use of a large number of nailing heads, since at least one nailing head and more often a plurality of nailing heads must be provided to nail each deck board, but also requires heavy duty components for producing articles having long stringers with a large number of deck boards, as for example long sections of dock or fence structures. The heavy duty construction is required as a consequence of the large mechanical forces exerted by the weight of the increased number of deck boards stacked in the hopper for holding down the lowermost deck board being nailed to the stringers. These requirements not only result in an expensive machine but also one in which the possibility of malfunction is increased because of the greater number of nailing heads which must be operated.
An additional problem in many automatic and semiautomatic assembly and nailing machines is their failure to permit ready adjustment to the parts and control devices of the machine for accommodating stringers and slats of varying sizes and shapes and for readily adjusting the positioning of the stringers and slats relative one another to enable the manufacture of assembled structures of varying sizes and configurations.
The present invention overcomes these problems and shortcomings of the prior art by providing a simple, reliable and relatively inexpensive apparatus for automatically assembling transverse slats to longitudinally advancing stringers by using a minimum number of nailing heads operative in repetitive stitch nailing fashion, and which is rapidly adjustable for accommodating slats and stringers of varied dimensions and for manufacturing articles of various sizes and configurations. While the present invention will be described with reference to a specific embodiment thereof employing a given number of stringers and nailing heads it will be understood that the invention is not limited to this specific embodiment but includes any number of such stringers and nailing heads. Further, while the present invention as described employs a particular electromechanical control system, it will be understood that other control systems which perform equivalent functions necessary to the operation of the apparatus may be used without departing from the spirit or intent of this invention.